Microelectromechanical systems (MEMS) devices at different pressures

ABSTRACT

The present disclosure relates to a method of forming a micro-electro mechanical system (MEMs) structure. In some embodiments, the method may be performed by providing a device substrate having a first MEMS device and a second MEMS device, and by providing a capping structure having a first cavity and a second cavity. The capping structure is bonded to the device substrate, such that the first cavity is arranged over the first MEMS device and the second cavity is arranged over the second MEMS device. A first pressure is established within the first cavity and the second cavity. A vent is selectively etched within the capping structure to change the first pressure within the second cavity to a second pressure, which is different from the first pressure.

REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No. 14/557,513filed on Dec. 2, 2014, which claims priority to U.S. ProvisionalApplication No. 62/076,579 filed on Nov. 7, 2014. The contents of theabove-referenced matters are hereby incorporated by reference in theirentirety.

BACKGROUND

Recent developments in the semiconductor integrated circuit (IC)technology include microelectromechanical system (MEMS) devices. MEMSdevices include mechanical and electrical features formed by one or moresemiconductor manufacturing processes. Examples of MEMS devices includemicro-sensors, which convert mechanical signals into electrical signals;micro-actuators, which convert electrical signals into mechanicalsignals; and motion sensors, which are commonly found in automobiles(e.g., in airbag deployment systems). For many applications, MEMSdevices are electrically connected to application-specific integratedcircuits (ASICs), and to external circuitry, to form complete MEMSsystems. Commonly, the connections are formed by wire bonding, but otherapproaches are also possible.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of a semiconductor device thatincludes microelectromechanical system (MEMS) devices in accordance withsome embodiments.

FIGS. 2A-2C illustrate flow charts of some embodiments of a method formanufacturing a semiconductor device in accordance with someembodiments.

FIG. 3 illustrates a cross-sectional view of some embodiments of asemiconductor device in accordance with multiple MEMS cavities.

FIG. 4 illustrates a flow chart of some embodiments of a method formanufacturing a semiconductor device in accordance with multiple MEMScavities.

FIGS. 5A-5M illustrate some embodiments of a series of cross-sectionalviews that collectively depict formation of a semiconductor device inaccordance with multiple MEMS cavities.

FIGS. 6A-6B illustrates a cross-sectional view of semiconductor deviceswith multiple MEMS cavities.

FIG. 7 illustrates a flow chart of some embodiments a semiconductordevice with multiple MEMS cavities.

FIGS. 8A-8F illustrate a series of some embodiments of cross-sectionalviews that collectively depict formation of a semiconductor device withmultiple MEMS cavities.

FIGS. 9A-9B illustrate some embodiments of a MEMS accelerometer.

FIGS. 10A-10B illustrate some embodiments of a MEMS gyroscope.

FIGS. 11A-11F illustrate cross-sectional views of various embodiments ofa semiconductor device with multiple MEMS cavities.

FIGS. 12A-12D illustrate cross-sectional views of various embodiments ofa semiconductor device with multiple MEMS cavities.

FIGS. 13A-13B illustrate cross-sectional views of various embodiments ofa semiconductor device with multiple MEMS cavities.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Moreover, “first”, “second”, “third”, etc. may be used herein for easeof description to distinguish between different elements of a figure ora series of figures. “First”, “second”, “third”, etc. are not intendedto be descriptive of the corresponding element. Therefore, “a firstsubstratelectric layer” described in connection with a first figure maynot necessarily corresponding to a “first substratelectric layer”described in connection with another figure.

Multiple MEMs device may be integrated onto a same integrated chip inrecent generations of MEMs ICs. For example, motion sensors are used formotion-activated user interfaces in consumer electronics such assmartphones, tablets, gaming consoles, smart-TVs, and in automotivecrash detection systems. To capture a complete range of movements withina three-dimensional space, motion sensors often utilize an accelerometerand a gyroscope in combination. The accelerometer detects linearmovement. The gyroscope detects angular movement. To meet consumerdemand for low cost, high quality, and small device footprint, theaccelerometer and the gyroscope can be formed frommicroelectromechanical system (MEMS) devices, which are integratedtogether on a same substrate. Although they share the same substrate,and hence a same manufacturing process, the accelerometer and thegyroscope utilize different operating conditions. For example, thegyroscope is often packaged in a vacuum for optimal performance. Incontrast, the accelerometer is often packaged at a predeterminedpressure (e.g., 1 atmosphere) to produce a smooth frequency response.

Therefore, the present disclosure is directed to multiple MEMS devicesthat are integrated together on a single substrate. A device substratecomprising first and second micro-electro mechanical system (MEMS)devices is bonded to a capping structure. The capping structurecomprises a first cavity arranged over the first MEMS device and asecond cavity arranged over the second MEMS device. The first cavity isfilled with a first gas at a first gas pressure. The second cavity isfilled with a second gas at a second gas pressure, which is differentfrom the first gas pressure. A recess is arranged within a lower surfaceof the capping structure. The recess abuts the second cavity. A vent isarranged within the capping structure. The vent extends from a top ofthe recess to the upper surface of the capping structure. A lid isarranged within the vent and configured to seal the second cavity. Otherembodiments are also disclosed.

FIG. 1 illustrates a cross-sectional view of a semiconductor device 100that includes first and second MEMS devices 104A, 104B arranged over adevice substrate 102. A capping structure 106 is bonded to the devicesubstrate 102. The capping structure 106 includes a first cavity 108Aencasing the first MEMS device 104A, and a second cavity 108B encasingthe second MEMS device 104B. The first or second MEMS device 104A, 104Bmay include, for example, a microphone, a gas pressure sensor, anaccelerometer, a gyroscope, or any other device that interfaces with theexternal environment. In one embodiment, the first MEMS device 104Aincludes an accelerometer, and the second MEMS device 104B includes agyroscope, which together form a motion sensor for a motion-activateduser interface or for an automotive crash detection system.

Hermetic seal boundaries 110A-110C are formed between the devicesubstrate 102 and the capping structure 106, such that the first andsecond cavities 108A, 108B can support pressures that are different fromone another. It is appreciated that while the first and second cavities108A, 108B share hermetic seal boundary 110C, other embodiments includefirst and second cavities 108A, 108B that do not share a common hermeticseal boundary. It is further appreciated other embodiments include asemiconductor device that includes three or more MEMS devices arrangedwithin three or more cavities, where at least two of the cavities areindependently maintained at gas pressures which are different from oneanother.

A recess 112 is arranged within the capping structure 106 in an uppersurface 120 of the second cavity 108B. In some embodiments, the recess112 may be located over the second MEMS device 104B. A vent 114 isformed through the capping structure 106, which vertically connects withthe recess 112. The vent 114 and recess 112 collectively connect thesecond cavity 108B to an ambient environment that surrounds thesemiconductor device 100. When unfilled, the vent 114 permits a secondgas pressure within the second cavity 108B to be adjusted relative to afirst gas pressure within the first cavity 108A. As a result, the secondgas pressure is different from the first gas pressure. A lid 116 isformed within the vent 114 and/or over an upper surface 118 of thecapping structure 106. The lid 116 forms a hermitic seal with sidewallsof the vent 114 and/or the upper surface 118 of the capping structure106 to seal the second cavity 108B from the ambient environment.

In some embodiments, a first width 122 of the vent 114 is significantlyless than a second width 124 of the recess 112. In such embodiments, thevent 114 is narrow enough that adhesive forces between surfaces of thelid 116 and surfaces of the capping structure 106, as well as surfacetension of material that forms the lid 116, prevents the material from“falling through” the vent 114 and contaminating the second MEMS device104B.

By independently controlling the pressures within the first and secondcavities 108A, 108B, performance of the semiconductor device 100 can beimproved. For example, performance of a motion sensor having a firstMEMS device 104A including an accelerometer, and a second MEMS device104B including a gyroscope can be increased by independently controllingthe pressures within the first and second cavities 108A, 108B, whichindependently optimizes function of the first and second MEMS devices104A, 104B (i.e., the accelerometer and the gyroscope).

FIGS. 2A-2C illustrate flow charts of some embodiments of a method formanufacturing the semiconductor device with multiple MEMS cavities.

FIG. 2A illustrates a flow chart of some embodiments of a method 200 formanufacturing the semiconductor device of FIG. 1.

At 202, a device substrate is provided. The device substrate includesfirst and second MEMS devices.

At 204, a capping structure is provided. The capping structure includesfirst and second cavities formed within its lower surface.

At 206, the capping structure is bonded to the device substrate. Uponbonding, the first cavity is arranged over the first MEMS device and thesecond cavity is arranged over the second MEMS device.

At 208, the first and second cavities are filled with a first gas at afirst gas pressure.

At 210, the pressure within the second cavity is changed to a second gaspressure, which is different from the first gas pressure.

FIG. 2B illustrates some further embodiments of bonding the cappingstructure to the device substrate (206 of method 200).

At 206A, a first hermetic seal is formed. The first hermetic sealsurrounds the first cavity at a first interface between a lower surfaceof the capping structure and an upper surface of the device substrate.The first hermetic seal prevents the first gas from diffusing from thefirst cavity.

At 206B, a second hermetic seal is formed. The second hermetic sealsurrounds the second cavity at a second interface between the lowersurface of the capping structure and the upper surface of the devicesubstrate. The second hermetic seal prevents the second gas fromdiffusing from the second cavity. Examples of first and second hermeticseals are given herein.

FIG. 2C illustrates some further embodiments of changing the gaspressure within the second cavity (210 of method 200).

At 210A, an opening is created within an upper surface of the secondcavity. The opening forms a vent through the capping structure. The ventconnects the second cavity to an ambient environment that surrounds thesemiconductor device.

At 210B, a gas pressure of the ambient environment is changed to thesecond gas pressure. As a result, gas diffusion through the vent betweenthe ambient environment and the second cavity changes the gas pressurewithin the second cavity to be equal to the second gas pressure.

At 210C, a lid is formed over the vent, which seals the second cavity atthe second gas pressure.

FIG. 3 illustrates some embodiments of a cross-sectional view of asemiconductor device 300 with multiple MEMS cavities. The semiconductordevice 300 comprises a device substrate 102, which is bonded to acapping structure 106. The device substrate 102 includes a processedsubstrate 306 and a MEMS substrate 308, which are bonded together. Theprocessed substrate 306 includes one or more active elements 310 (e.g.,a transistor), comprising first and second source/drain regions 309A,309B, which are separated by a channel region 311 arranged below a gate313. A series of metallization planes 312 and via interconnects 314connect to the one or more active elements 310. In some embodiments, theprocessed substrate 306 includes a semiconductor substrate 302. Themetallization planes 312 and the via interconnects 314 are arrangedwithin an inter-metal dielectric (IMD) material 304 formed over an uppersurface of the semiconductor substrate 302.

The MEMS substrate 308 includes a semiconductor material or anon-semiconductor material. In some embodiments, the MEMS substrate 308includes the same material that is used for the semiconductor substrate302. In some embodiments, the MEMS substrate 308 includes asemiconducting material different from that of the semiconductorsubstrate 302. The MEMS substrate 308 has an upper surface 320 that isbonded to the capping structure 106, and an opposite, lower surface 322that is bonded to an upper surface 324 of the IMD material 304. The MEMSsubstrate 308 includes first and second MEMS devices 104A, 104B, whichare arranged within first and second cavities 108A, 108B. The first andsecond cavities 108A, 108B are formed between the device substrate 102and the capping structure 106. In some embodiments, the first and secondcavities 108A, 108B extend into the device substrate 102. For instance,as shown on FIG. 3, the first and second cavities 108A, 108B extend intothe IMD material 304 to provide clearance for movable parts of the firstor second MEMS device 104A, 104B. In other embodiments, the first andsecond cavities 108A, 108B extend into the semiconductor substrate 302.

First through third hermetic seal boundaries 110A-110C are formedbetween the device substrate 102 and the capping structure 106, suchthat the first and second cavities 108A, 108B can support gas pressuresthat are different from one another. For the embodiments of thesemiconductor device 300 the first through third hermetic sealboundaries 110A-110C comprise one or more bonding materials 326.

The capping structure 106 may be utilized in wafer level chip scalepackage (WLCSP) technology (e.g., which packages an integrated chip at awafer level, rather than after singulation) to lower fabrication costsand to achieve a smaller substrate size. The capping structure 106 ofsemiconductor device 300 includes a re-distribution layer (RDL) ofconductive material (e.g., low resistance silicon) to provide forelectrical routing (e.g., lateral routing) along the capping structureto an input/output (I/O) connection point of a semiconductor device 300.Within the capping structure 106, an isolation trench 334 encloses a lowresistance conductive pillar 336 (e.g., Si-pillar). The isolation trench334 electrically isolates the low resistance conductive pillar 336 froma remainder of the capping structure 106. The first through thirdhermetic seal boundaries 110A-110C are also conductive. As a result, thelow resistance pillar 336 provides an electrical conduction path from atop surface of the capping structure 106, through the hermetic sealboundaries 110A, 110C to the MEMS substrate 308. The second hermeticseal 110B is not connected to a pillar 336. The second hermetic seal110B is connected to a guard ring 350 of the capping structure 106,which seals the first and second cavities 108A, 108B, and provides anelectrical path between the capping structure 106 and the MEMS substrate308.

By providing a conductive path from the MEM substrate 308 to the topsurface of the capping structure 106, the low resistance pillar 336enable semiconductor device 300 to be manufactured by way of the WLCSPtechnology. This is because the low resistance pillar 336 allows for anelectrical connection between the MEM substrate 308 and an externalcircuits without additional packaging operations. For example, the lowresistance pillar 336 allows for an external connection (e.g., awirebonding or flip chip solder ball) to be formed on the upper surfaceof the capping structure 106 (e.g., on top of the pillars 336) prior tosingulation of the device substrate 102.

The isolation trench 334 of the semiconductor device 300 is filled withsilicon 338 (e.g., poly-Si) and dielectric material 340 (e.g., SiO2).The silicon 338 provides a conductive path in parallel with the pillar336. The dielectric material 340 electrically isolates the pillar 336within the capping structure 106. A solder bump (not shown) may bearranged onto a top of the pillar 336 to provide a connection pointbetween the pillar 336 and an external circuit (e.g., a system levelprinted circuit board (PCB)), to which the capping structure 106 may bemounted after chip dicing.

The processed substrate 306 and the MEMS substrate 308 may be bonded byeutectic bonds 328, which comprise a bottom bond pad 330 (e.g., Al, Cu,Ti, Ta, Au, Ni, Sn) arranged on the upper surface 324 of the IMDmaterial 304, and a top bond pad 332 (e.g., Ge, Si) arranged below thelower surface 322 of the MEMS substrate. The eutectic bonds 328 connectthe MEMS substrate 308 to the active elements 310 of the processedsubstrate 306 through the metallization planes 312 and the viainterconnects 314. MEMS contact pads 342 are arranged on the top of theMEMS substrate 308 above the eutectic bonds 328. The MEMs contact pads342 provide for an area electrical connection between the processedsubstrate 306 and the MEMs substrate 308. The MEMS contact pads 342comprise a top pad layer 344 (e.g., TiN) disposed over a bottom pad 346(e.g., AlCu). The MEMS contact pads 342 provide an electrical connectionbetween the processed substrate 306 and the MEMS substrate 308. In someembodiments, the processed substrate 306 and the MEMS substrate 308 areconnected through a via. In some embodiments, the MEMS substrate 308 isnot connected to active elements 310 of the processed substrate 306. Inother embodiments, the MEMS substrate 308 is not connected to theprocessed substrate 306.

A vent 114 vertically extends through the capping structure 106 toconnect the second cavity 108B to an ambient environment that surroundsthe semiconductor device 300. The vent 114 permits a second gas pressurewithin the second cavity 108B to be independently adjusted relative to afirst gas pressure within the first cavity 108A. A lid 116 is arrangedwithin the vent 114 and/or over an upper surface 118 of the cappingstructure 106 to seal the second cavity 108B. The lid 116 forms ahermitic seal with sidewalls of the vent 114 and/or the upper surface118 of the capping structure 106.

FIG. 4 illustrates a flow chart of some embodiments of a method 400 formanufacturing a semiconductor device with multiple MEMS cavities byusing a wafer level chip scale package (WLCSP).

At 402, a masking layer is selectively formed over a capping substrate.The capping substrate is conductive (e.g., low resistance Si).

At 404, a pillar of capping substrate material is formed by performingone or more first etch processes to a lower surface of the cappingsubstrate. The one or more first etch processes produce an isolationtrench, which extends into the lower surface of the capping substrateand surrounds the pillar.

At 406, isolation material is formed onto the lower surface and withinthe isolation trench of the capping structure according to the maskinglayer, and conductive material is formed within the isolation trench.The isolation material may sandwich the conductive material within theisolation trench, so as to isolate the pillars of capping substratematerial from a remainder of the capping substrate and form conductivepaths that run in parallel to the pillar.

At 408, first and second cavities are formed within the lower surface ofthe capping substrate by performing one or more second etch processes tothe lower surface. In some embodiments, the one or more second etchprocesses are performed simultaneously with the one or more first etchprocesses.

At 410, a recess is formed within an upper surface of the second cavity(i.e., the lower surface of the capping substrate).

At 412, an upper surface of the capping substrate is thinned (e.g., by agrinding the upper surface), which exposes the isolation trench. As aresult, the pillar extends from the lower surface capping substrate,through the capping substrate, to the upper surface of the cappingsubstrate. The pillar is surrounded and isolated from a remainder of thecapping substrate by the isolation trench.

At 414, the capping substrate is bonded to a device substrate by forminga first and second hermetic seals between the capping structure and thedevice substrate. The device substrate comprises a processedsemiconductor substrate (e.g., a Si wafer with active elements 310)bonded to a MEMS substrate, which contains first and second MEMS devices(e.g., an accelerometer and a gyroscope). The first and second hermeticseals surround the first and second cavities. Examples of hermetic sealsinclude, but are not limited to eutectic bonds, fusion bonds, thermalcompressive bonds, and the like.

At 416, an opening is created within the recess. The opening and recesscollectively form a vent through the capping structure. The ventconnects the second cavity to an ambient environment that surrounds thesemiconductor device. As a result, gas diffuses through the vent betweenthe ambient environment and the second cavity to bring the second cavityto a second gas pressure.

At 418, a hermitic seal is formed between a lid and sidewalls of thevent and the upper surface of the capping substrate to seal the secondcavity at the second gas pressure.

FIGS. 5A-5M illustrate some embodiments of a series of cross-sectionalviews that collectively depict formation of a semiconductor device withmultiple MEMS cavities. Although FIGS. 5A-5M are described in relationto the method 400, it will be appreciated that the structures disclosedin FIGS. 5A-5M are not limited to the method 400, but instead may standalone as structures independent of the method 400. Similarly, althoughthe method 400 is described in relation to FIGS. 5A-5M, it will beappreciated that the method 400 is not limited to the structuresdisclosed in FIGS. 5A-5M, but instead may stand alone independent of thestructures disclosed in FIGS. 5A-5M.

FIG. 5A illustrates a cross sectional view of a capping substrate 506corresponding to act 402. A silicon nitride (SiN) masking layer has beendeposited and patterned to form first through third deposited SiNregions 502A-502C. In some embodiments, deposition of the SiN layerinvolves chemical vapor deposition (CVD), sputtering, or otherappropriate deposition process. Patterning of the first through thirddeposited SiN regions 502A-502C involves photolithography and etching.

In FIG. 5B, which corresponds to act 404, isolation trenches 510 havebeen formed through photolithography and etching of the lower surface508 of the capping substrate 506. In some embodiments, the etchsimultaneously produces first and second cavities 108A, 108B within thelower surface 508 of the capping substrate 506. In some embodiments, aseparate, second etch produces the first and second cavities 108A, 108B(as illustrated in FIG. 5G), in order to prevent oxidation of thesidewalls, during the oxidation process of FIG. 5C.

In FIG. 5C, which corresponds to act 406, an oxidation layer 512 (e.g.,SiO₂) has been formed on the lower surface 508 of the capping substrate506 and along sidewalls and bottom surfaces of the isolation trenches510. In some embodiments, the oxidation layer 512 is formed by thermaloxidation of the capping substrate 506 in a furnace environment. Theoxidation layer 512 does not form on areas of the lower surface 508 ofthe capping substrate 506 that are covered by the first through thirddeposited SiN regions 502A-502C.

In FIG. 5D, which corresponds to act 406, the first through thirddeposited SiN regions 502A-502C have been removed. In variousembodiments, removal of the first through third deposited SiN regions502A-502C is accomplished by a reactive ion etching (RIE) process, or aselective etch.

In FIG. 5E, which corresponds to act 406, the isolation trenches 510have been filled with polysilicon 514, which extends over the lowersurface 508 of the capping substrate 506. In various embodiments, thepolysilicon 514 is formed by CVD (e.g., low-pressure CVD (LPCVD) orplasma-enhanced CVD (PECVD)), physical vapor deposition (PVD), atomiclayer deposition (ALD), molecular beam epitaxy (MBE), electron beam(e-beam) epitaxy, or other appropriate process. The polysilicon 514 isused to make an electrical contact with a pillar (336), which issubsequently formed below it within the capping substrate 506.

In some embodiments, shown in FIG. 5F, a metal layer 518 (e.g., Ge) hasbeen disposed over the polysilicon 514 (e.g., through sputtering). Themetal and polysilicon 514 have then been patterned and etched throughphotolithography and etching to form polysilicon stand-offs 516, whichare physically and electrically connected to the polysilicon in theisolation trenches 510. The polysilicon stand-offs 516 serve aselectrical conduction paths in parallel with the subsequently formedpillar (336). The remaining portions of the metal layer 518 are arrangedon the polysilicon stand-offs 516 and are configured to form part of aeutectic bond between the capping substrate 506 and a device substrate.

In FIG. 5G, which corresponds to act 408, first and second cavities108A, 108B have been etched within the lower surface 508 of the cappingsubstrate 506. In various embodiments, the etch that produces the firstand second cavities 108A, 108B can be performed simultaneously with theetch that produced the isolation trenches 510 (in FIG. 5B), or the etchthat produced the polysilicon stand-offs 516 (in FIG. 5F).

In FIG. 5H, which corresponds to act 410, a recess 112 has been formedwithin the lower surface 508 of the capping substrate 506 (i.e., uppersurface of the second cavity) through photolithography and etching ofthe lower surface 508 of the capping substrate 506 (act 408 of method400).

In FIG. 5I, which corresponds to act 412, the capping substrate 506 hasbeen flipped over and thinned though a grinding process, such as achemical mechanical polish (CMP), to produce the capping structure 106.

In FIG. 5J, which corresponds to act 414, the capping structure 106 hasbeen bonded to a device substrate 102. The device substrate 102 includesa processed substrate 306, which is bonded to a MEMS substrate 308. Thebonding forms a first hermetic seal comprising the first and secondhermetic seal boundaries 110A, 110B. The first hermetic seal surroundsthe first cavity 108A at an interface between the lower surface 508 ofthe capping structure 106 and the upper surface 320 of the devicesubstrate 102 (of the MEMS substrate 308). Simultaneously, bonding formsa second hermetic seal comprising the second and third hermetic sealboundaries 110B, 110C. The second hermitic seal surrounds the secondcavity 108B at an interface between the lower surface 508 of the cappingstructure 106 and the upper surface 320 of the device substrate 102.Examples of heretic seals include thermal compressive bonding, fusionbonding, and eutectic bonding with one or more bonding materials.Various examples of bonding material 326 and bonding schemes between thecapping structure 106 and the device substrate 102 are illustrated inFIGS. 11A-11F.

In some embodiments, the processed substrate 306 and capping structurehave a same doping type. In various embodiments, the processed substrate306 is an elementary semiconductor, a compound semiconductor, or analloy semiconductor. Examples of elementary semiconductors include, butare not limited to, one or more of silicon and germanium. Examples ofcompound semiconductors include, but are not limited to, one or more ofsilicon carbide, gallium arsenide, gallium phosphide, indium phosphide,indium arsenide, and indium antimonide. Examples of alloy semiconductorsinclude, but are not limited to, one or more of SiGe, GaAsP, AlInAs,AlGaAs, GaInAs, GaInP, and GaInAsP. In some embodiments, the processedsubstrate 306 includes a non-semiconductor material. Examples ofnon-semiconductor materials include, but are not limited to, one or moreof glass, fused quartz, and calcium fluoride.

In FIG. 5K, which corresponds to act 416, a vent 114 has been formed theupper surface of the second cavity 108B. In some embodiments, the vent114 is formed through photolithography and etching of the upper surface520 of the capping substrate 506. The vent 114 connects the secondcavity 108B to an ambient environment surrounding the capping structure106 and the device substrate 102. In some embodiments, the vent 114 isnarrower than the recess 112.

Upon formation of the vent 114, a gas pressure of the ambientenvironment is changed to the second gas pressure. In some embodiments,the capping structure 106 and device substrate 102 may be bonded in aprocessing chamber, and the gas pressure of the ambient environment ischanged in situ. For example, the gas pressure within the processingchamber is maintained at the first gas pressure throughout theprocessing steps illustrated in FIGS. 5A-5K. Then, after formation ofthe vent 114 in FIG. 5K, the gas pressure within the processing chamberis adjusted to the second gas pressure. Gas diffusion is allowed tooccur through the vent 114 between the ambient environment and thesecond cavity 108B. Once the gas diffusion reaches a steady-statecondition, the gas pressure within the second cavity 108B is equal tothe second gas pressure.

In FIG. 5L, which corresponds to act 418, a conformal layer of lidmaterial 524 has been disposed over the upper surface 520 of the cappingstructure 106 (act 416 of method 400). In various embodiments, the lidmaterial 524 comprises SiN, SiON, oxide, photoresist (PR), polyimide,amorphous carbon (a-C), polysilicon, amorphous silicon (a-Si), metal(e.g. AlCu etc.) epoxy, or other suitable material. The suitability ofthe lid material 524 is determined by several factors, including, butnot limited to, the material used to form the capping structure 106 andthe second gas pressure within the second cavity 108B. Otherconsiderations for the suitability of the lid material 524 include athermal budget of forming the semiconductor device 300, which may resultin softening of the lid material 524. For a second gas pressure of lessthan about 3 torr, the lid material 524 may comprise a metal film (e.g.,formed via sputtering). For a second gas pressure in a range of about 3torr to about 100 torr the lid material 524 may comprise oxide, SiN,SiON, or a-C (e.g., formed via CVD). For a third gas pressure in a rangeof about 100 torr to about 500 torr the lid material 524 may comprisepolysilicon. For a fourth gas pressure in a range of about 500 torr toabout 1,000 torr the lid material 524 may comprise PR, polyimide orepoxy (e.g., formed via a UV cure technique), or a CVD oxide (e.g.,formed under atmospheric pressure (APCVD)).

In FIG. 5M, which corresponds to act 418, the lid material 524 has beenpatterned through photolithography and etching to form a lid 116, whichis arranged over a first portion 522A of the upper surface 520 of thecapping structure 106 in a vicinity of the vent 114. The removed lidmaterial 524 exposes a second portion 522B of the upper surface 520 ofthe capping structure 106. The lid 116 forms a hermitic seal between thelid and sidewalls of the vent 114 and the upper surface 520 of thecapping structure 106 to seal the second cavity 108B at the second gaspressure. For some embodiments of semiconductor device 300, the vent 114is narrower than the recess 112. As a result, the vent 114 is narrowenough that adhesive forces between surfaces of the lid 116 and surfacesof the capping structure 106, as well as surface tension of materialthat forms the lid 116, prevents the material from “falling through” thevent 114 and contaminating the second MEMS device 104B.

FIGS. 6A-6B illustrate some embodiments of semiconductor devices formedusing some non-WLCSP process(es). While the WLCSP process integrates thewhole packing process by using the pillar 336, non-WLCSP processesutilize a cap wafer. The cap wafer is patterned and etched through oneor more lithography processes before bonding. The cap wafer is thenbonded to a device wafer formed from a singular die. Some examples ofnon-WLCSP process(es) include a partial die saw process, an onlygrinding process (OGP), and a grind to open process (GTO). In thepartial die saw process, a blade produces a reference cut along a scribeline of a wafer, the wafer is then thinned by a grind process, then thewafer is diced along the reference cut to exposure the pad area. The OGPor GTO processes can be alternatively used to singularize the wafer. TheOGP or GTO processes use grinding only.

FIG. 6A illustrates some embodiments of a cross-sectional view of asemiconductor device 600A. The semiconductor device 600A comprises adevice substrate 102, which is bonded to a capping structure 106. Theprocessed substrate 306 and the MEMS substrate 308 are bonded by fusionbonds formed at an interface 602 between the two. The fusion bondsconnect the MEMS substrate 308 to the active elements 310 of theprocessed substrate 306 through the metallization planes 312 and the viainterconnects 314, and through silicon vias (TSVs) 604. In at least oneembodiment, the TSVs 604 include tungsten (W). First through thirdhermetic seal boundaries 110A-110C are formed from one or more bondingmaterials 326. At least one of the TSVs 604 is configured for anelectrical connection to external circuitry. At least one of the TSVs604 is configured for an internal electrical connection (e.g., betweenthe MEMs substrate 308 and the active elements 310 of the devicesubstrate 102).

A vent 114 is arranged within the capping structure 106. Sidewalls 608of the vent 114 form a taper angle (θ) such that the vent is wider atits top (i.e., a first interface with the upper surface 520 of thecapping structure 106) than at its bottom (i.e., a second interface witha top of the recess 112).

A lid 116 is formed within the vent 114 and/or over an upper surface 118of the capping structure 106. The lid 116 forms a hermitic seal withsidewalls of the vent 114 and/or the upper surface 118 of the cappingstructure 106 to seal the second cavity 108B from the ambientenvironment. The narrow bottom of the vent 114 helps preventcontamination of the second MEMS device 104B by lid material bydecreasing an amount of a bottom surface 610 of the lid 116 that isexposed to the second cavity 108B. The bottom surface 610 of the lid 116is suspended by adhesive forces between surfaces of the lid 116 andsurfaces of the capping structure 106, as well as surface tension ofmaterial that forms the lid 116.

MEMS contact pads 342 are arranged on the top of the MEMS substrate 308above the interface 602. The MEMS contact pads 342 comprise a top padlayer 344 (e.g., TiN) disposed over a bottom pad (e.g., AlCu). The MEMScontact pads 342 improve the electrical interface between the TSVs 604and the MEMS substrate 308.

First and second cavities 108A, 108B are formed within the cappingstructure 106. The first and second cavities 108A, 108B cover first andsecond MEMS devices 104A, 104B, respectively. The first and secondcavities 108A, 108B also extend into the device substrate 102 (i.e., theIMD material 304) to permit movement of one or more moveable features ofthe first and second MEMS devices 104A, 104B. The first and secondcavities 108A, 108B are maintained at first and second gas pressures,respectively, which are different from one another.

FIG. 6B illustrates some embodiments of a cross-sectional view of asemiconductor device 600B, which includes external connection portions610B of the capping structure 106 (e.g., formed through an etch of thecapping structure 106). Trenches 608B separate the external connectionportions 610B from the cap portion 606B. As a result, first and fifthTSVs 604A, 604E form connections between the device substrate 102 andthe external circuitry, through the external connection portions 610B.Second through fourth TSVs 604B-604D form connections between theprocessed substrate 306 and the MEMS substrate 308.

In some embodiments, the external connection portions 610B areconfigured with a width smaller than a width of the first through fifthTSVs 604A-604E. In some embodiments, the external connection portions610B have a width of 50 μm and smaller. Compared to other approacheswhere TSVs are formed with a width of at least 90 μm, such embodimentspermit a greater number of input/outputs (I/Os) to be formed and/orpermit increased flexibility in I/O arrangement within a presetsubstrate area.

FIG. 7 illustrates a flow chart of some embodiments of a method 700 formanufacturing the semiconductor device of FIG. 6 using a non-wafer levelchip scale package (WLCSP).

At 702, a device substrate and a capping substrate are provided. In someembodiments, the device substrate comprises a semiconductor substratethat is bonded to a MEMS substrate containing first and second MEMSdevices. In some embodiments, the semiconductor substrate iselectrically connected to the MEMS substrate by one or more TSVs.

At 704, one or more first etch processes are performed to a lowersurface of the capping substrate to form first and second cavitieswithin the lower surface of the capping substrate.

At 706, a recess is formed within an upper surface of the second cavity(i.e., and the lower surface of the capping substrate).

At 708, the capping substrate is bonded to the device substrate, to forma capping structure, by forming first and second hermetic seals. Thefirst and second hermetic seals surround the first and second cavities,respectively, and maintain a first gas pressure within the first andsecond cavities.

At 710, one or more second etch processes may be optionally performed toan upper surface of the capping substrate. The one or more second etchprocesses etch completely through the capping substrate, which separatesthe capping substrate into two or more portions that are isolated fromone another by trenches formed by the one or more second etch processes.The two or more portions include an external connection portion, whichforms an electrical connection from the device substrate to externalcircuitry. The two or more portions also include the a cap portion,wherein the first and second cavities are formed.

At 712, a gas pressure within the second cavity is changed to a secondgas pressure, which is different from the first gas pressure.

FIGS. 8A-8F illustrate some embodiments of a series of cross-sectionalviews that collectively depict formation of a semiconductor device.Although FIGS. 8A-8F are described in relation to the method 700, itwill be appreciated that the structures disclosed in FIGS. 8A-8F are notlimited to the method 700, but instead may stand alone as structuresindependent of the method 400. Similarly, although the method 700 isdescribed in relation to FIGS. 8A-8F, it will be appreciated that themethod 700 is not limited to the structures disclosed in FIGS. 8A-8F,but instead may stand alone independent of the structures disclosed inFIGS. 8A-8F.

FIG. 8A illustrates a cross-sectional view corresponding to act 802. Asshown in FIG. 8A, a processed substrate 306 is provided, which has beenprepared through one or more fabrication processes. For example, theprocessed substrate 306 includes one or more active elements 310. Aseries of metallization planes 312 and via interconnects 314 connect tothe one or more active elements 310. The processed substrate 306includes a semiconductor substrate 302, and an IMD material 304 formedover an upper surface of the semiconductor substrate 302. First andsecond substrate cavities 802A, 802B are formed in a top portion of theIMD material 304 corresponding to first and second MEMS devices thatwill be subsequently positioned over the first and second substratecavities 802A, 802B. In some embodiments, the first and second substratecavities 802A, 802B are formed by one or more of a wet etching processor a dry etching process.

FIG. 8B illustrates a cross-sectional view corresponding to act 802. Asshown in FIG. 8B, a MEMS substrate 308 has been bonded to the processedsubstrate 306 to form a device substrate 102. For example, the MEMSsubstrate 308 is bonded to the processed substrate 306 by a fusionbonding process at interface 602. In some embodiments, a fusion bondingis achieved between the IMD material 304 comprising SiO₂ and the MEMSsubstrate 308 comprising Si. In some embodiments, the MEMS substrate 308is thinned down to reduce the thickness thereof after fusion bondingwith the processed substrate 306

In FIG. 8C, which corresponds to act 802, first and second MEMS devices104A, 104B, bonding materials 326, bottom pads 346 (e.g., Al, Cu, etc.),and TSVs 604 have been formed. The bonding materials 326 are used toform a hermetic seal between the MEMS substrate 308 and a cappingstructure that will be later positioned over the device substrate 102.The bottom pads 346 improve an electrical connection between the TSVs604 and the MEMS substrate 308. To form the TSVs 604, trenches have beenformed through the IMD material 304, which reach the metallizationplanes 312. The trenches have then been filled with metal (e.g., W) toform the TSVs 604, which are electrically connected to the metallizationplanes 312. The bonding materials 326 and bottom pads 346 have beenformed from one or more layers (e.g., AlCu), which has been depositedover the MEMS substrate 308 and patterned. The first and second MEMSdevices 104A, 104B have been formed from the MEMS substrate 308 byvarious processes including photolithography and etching processes.

FIG. 8D illustrates a cross-sectional view corresponding to acts704-706. As shown in FIG. 8D, a capping structure 106 has been prepared.In some embodiments, the capping structure 106 is prepared from asilicon capping substrate that has been subjected to a first etch toform first and second cavities 108A, 108B (act 704 of method 700). Insome embodiments, bonding materials 326 are formed on portions of thecapping structure 106 to form a hermetic seal with the device substrate102. The capping structure has been further prepared by performing asecond etch to form a recess 112 within a surface of the second cavity108B (act 706 of method 700).

In FIG. 8E, which corresponds to act 708, the capping structure 106 hasbeen flipped over and bonded to the device substrate 102. For example,the bonding materials 326 of the capping structure 106 are bonded by aeutectic bonding process to the corresponding bonding materials 326 ofthe device substrate 102, such that the device substrate 102 and thecapping structure 106 are physically and electrically connected throughthe bonding materials 326 and the TSVs 604. Upon bonding, the first andsecond substrate cavities 802A, 802B become part of the first and secondcavities 108A, 108B. In some embodiments, the capping structure 106 isthinned down to remove a partial thickness after being bonded to thedevice substrate 102.

In some embodiments, the eutectic bond 328 includes asemiconductor-to-metal bonding between a semiconductor material and ametal material. In some embodiments, the semiconductor material includesat least one of Ge, Si, SiGe, or another semiconductor material. In someembodiments, the metal material includes at least one of Al, Cu, Ti, Ta,Au, Ni, Sn, or another metal. Another example of eutectic bonding is ametal-to-metal bonding between two metal materials each including atleast one of Al, Cu, Ti, Ta, Au, Ni, Sn, or another metal. The materialsto be bonded are pressed against each other in an annealing process toform an eutectic phase of the materials. For example, a eutectic bindingbetween Ge and Al is formed at an annealing temperature in a range from400° C. to 450° C.

In FIG. 8F, which corresponds to act 712, a vent 114 has been formed inthe upper surface of the second cavity 108B. Upon formation of the vent114, the pressure of the ambient environment surrounding the cappingstructure 106 and the device substrate 102 is changed to the second gaspressure, and gas diffusion is allowed to occur through the vent 114between the ambient environment and the second cavity 108B. Once the gasdiffusion reaches a steady-state condition, the pressure within thesecond cavity 108B is equal to the second gas pressure. A conformallayer of lid material 524 has been disposed and patterned to form a lid116, which creates a hermitic seal to maintain the second cavity 108B atthe second gas pressure.

In some embodiments, the capping structure 106 is etched to formexternal connection portions (optional act 710 of method 700), which areisolated from the rest of the capping structure. The external connectionportions form connections between the device substrate 102 and theexternal circuitry.

FIGS. 9A-9B illustrate some embodiments of a capacitive MEMSaccelerometer 900. It is appreciated that the capacitive MEMSaccelerometer 900 is one possible type of MEMS accelerometer that isincluded for illustration purposes, and does not impose any limitationon the type of MEMS accelerometer utilized in conjunction with theembodiments of the present disclosure. The capacitive MEMS accelerometer900 includes first and second conductive plates 902A, 902B, which areoriented parallel to one another. A capacitance of the capacitive MEMSaccelerometer 900 is proportional to an area (A) of the first and secondconductive plates 902A, 902B, as well as a distance (d) between them.Therefore, the capacitance changes if the distance (d) between the firstand second conductive plates 902A, 902B changes. The second conductiveplate 902B is rigidly attached to an assembly 904. The first conductiveplate 902A is elastically attached to the assembly 904 by springs 906.

When the capacitive MEMS accelerometer 900 undergoes a linearacceleration event along the direction parallel to d, the secondconductive plate 902B moves with the assembly 904, while the firstconductive plate 902A initially does not. Instead, the springs 906expand, allowing the first conductive plate 902A to initially remainstationary. The resulting change in capacitance caused by the movementof the first conductive plate 902A relative to the second conductiveplate 902B can be used to determine a magnitude and direction of theacceleration.

Upon completion of the linear acceleration event, the first conductiveplate 902A will oscillate about an equilibrium position until a dampingeffect of air friction slows and eventually stops it. It is thereforedesirable in some embodiments to tune the damping effects of the airfriction to efficiently detect a first linear acceleration event, whiledamping oscillation from the first linear acceleration event in enoughtime to detect a subsequent linear acceleration event. The dampingeffects of the air friction can be tuned by a gas pressure of a gassurrounding the capacitive MEMS accelerometer 900. In some embodiments,a gas pressure on an order of about 1 atmosphere can achieve effectivedamping. It is further appreciated that the exemplary capacitive MEMSaccelerometer 900 of FIGS. 9A-9B is a “1-axis” accelerometer. In orderto detect a complete range of linear accelerations in athree-dimensional (3D) space, three or more orthogonally orientedcapacitive MEMS accelerometers 900 can be utilized together to form a“3-axis” accelerometer.

FIGS. 10A-10B illustrate some embodiments of a ring MEMS gyroscope 1000.FIG. 10A illustrates a top view of the ring MEMS gyroscope 1000. FIG.10B illustrates a cross-sectional view of the ring MEMS gyroscope 1000.It is appreciated that the ring MEMS gyroscope 1000 is one possible typeof MEMS gyroscope that is included for illustration purposes, and doesnot impose any limitation on the type of MEMS gyroscope utilized inconjunction with the embodiments of the present disclosure. The ringMEMS gyroscope 1000 includes an annular ring 1002. The annular ring 1002is supported in free-space by spokes 1004, which are attached at firstand second nodes 1006A, 1006B.

During operation of the ring MEMS gyroscope 1000, the annular ring 1002vibrates at a resonant frequency. Actuators or transducers (not shown)are attached to the upper surface of the annular ring 1002 at the firstand second nodes 1006A, 1006B, and are electrically connected to bondpads on the spokes 1004. The actuators or transducers drive the annularring 1002 into a mode of vibration at resonance. When the ring MEMSgyroscope 1000 is in a resonant state, and not subjected to any angularacceleration, first nodes 1006A move radially, while the second nodes1006B remain stationary. However, when the ring MEMS gyroscope 1000 issubjected to an angular acceleration event (e.g., rotation 1008), theCoriolis force changes the resonate state of the annular ring 1002,which causes the second nodes 1006B to move. By detecting the relativemovement first and second nodes 1006A, 1006B, the angular accelerationof the ring MEMS gyroscope 1000 can be measured.

Unlike the capacitive MEMS accelerometer 900, which oscillates during alinear acceleration event, the annular ring 1002 of the ring MEMSgyroscope 1000 is maintained in a resonant state while in operation. Assuch, the damping effects of air friction are not desired, as theyrequire additional power from the actuators or transducers to drive theannular ring 1002 into the resonant state. It is therefore desirable insome embodiments to negate the damping effects of the air friction toefficiently detect an angular acceleration event by sealing the ringMEMS gyroscope 1000 in a vacuum. The vacuum reduces a Q-factor of thering MEMS gyroscope 1000 by suppressing energy dissipation due to airfriction.

FIGS. 11A-11F illustrate cross-sectional views of various alternateembodiments of a disclosed semiconductor device having multiple MEMScavities.

FIG. 11A illustrates a cross-sectional view of some embodiments of asemiconductor device 1100A, in which locations of the pillar 336 and theguard rings 350 are reversed compared to the semiconductor device 300.As a result, the pillar 336 provides an external connection betweenactive element 1102A and external circuitry through the metallizationplanes 312 and the via interconnects 314. In a similar manner, activeelement 1104A is connected to first MEMS device 104A. The IMD material304 of the processed substrate 306 is bonded to the MEMS substrate 308by the eutectic bonds 328. In some embodiments, the eutectic bonds 328include a semiconductor-to-metal bonding between a semiconductormaterial 1106A and a metal material 1108A. The eutectic bonds 328, whichphysically and electrically connect the processed substrate 306 to theMEMS substrate 308.

FIG. 11B illustrates a cross-sectional view of some embodiments of asemiconductor device 1100B, in which the bonding materials 326 of thesemiconductor device 300 are replaced by eutectic bonds 328, whichinclude bottom bond pads 330 (e.g., Al, Cu, Ti, Ta, Au, Ni, Sn) on anupper surface of the IMD material 304, and the top bond pads 332 (e.g.,Ge, Si) on the silicon 338 of the capping structure 106.

FIG. 11C illustrates a cross-sectional view of some embodiments of asemiconductor device 1100C, in which connections between the active andpassive elements of the semiconductor substrate 302 and the MEMSsubstrate 308, and/or external circuitry (i.e., through pillars 336) areformed by TSVs 604, which are connected to the metallization planes 312and via interconnects 314 of the device substrate 102.

FIG. 11D illustrates a cross-sectional view of some embodiments of asemiconductor device 1100D, in which the IMD material 304 of theprocessed substrate 306 and the MEMS substrate 308 are bonded by afusion bond 1102D. An example of fusion bonding process involvespressing the processed substrate 306 and the MEMS substrate 308 againsteach other and performing an annealing process to cause the processedsubstrate 306 and the MEMS substrate 308 to be bonded together due toatomic attraction forces. The fusion bonding process is applicable forSiO₂ to Si bonding, Si to Si bonding, and other suitable bonding. In oneor more embodiments, SiO₂ to Si fusion bonding occurs between the IMDmaterial 304 (e.g., SiO₂) and the MEMS substrate 308 (e.g., Si).

FIG. 11E illustrates a cross-sectional view of some embodiments of asemiconductor device 1100E, in which a first active element 310A isconnected to the MEMS substrate 308 (e.g., the first or second MEMSdevices 104A, 104B) by a first TSV 604A. Second active element 310B isconnected to external circuitry through TSV 604B and pillar 336A. TheMEMS substrate (e.g., the first or second MEMS devices 104A, 104B) areconnected to external circuitry by pillar 336B.

FIG. 11F illustrates a cross-sectional view of some embodiments of asemiconductor device 1100F including a device substrate 102, but noprocessed substrate 306. The semiconductor device 1100F contains noactive or passive elements. Internal connections are made within theMEMS substrate 308. Connections to external circuitry (e.g., from thefirst and second MEMS devices 104A, 104B) are made through the pillars336 of the capping structure 106.

FIGS. 12A-12D illustrate cross-sectional views of various alternateembodiments of a disclosed semiconductor device having multiple MEMScavities.

FIG. 12A illustrates a cross-sectional view of some embodiments of asemiconductor device 1200A, in which first through third hermetic seals110A-110C have been formed from eutectic bonds 328. The processedsubstrate 306 has been bonded to the MEMS substrate 308 with a fusionbond.

FIG. 12B illustrates a cross-sectional view of some embodiments of asemiconductor device 1200B, in which the bond type at a first interfacebetween the processed substrate 306 and the MEMS substrate 308, and at asecond interface between the MEMS substrate 308 and the cappingstructure 106 have been reversed. The first through third hermetic sealsboundaries 110A-110C have been formed from fusion bonds. The processedsubstrate 306 has been bonded to the MEMS substrate 308 with eutecticbonds 328. It is appreciated that additional embodiments including allpossible combinations of fusion and eutectic bonding at the first andsecond interfaces are within the contemplated scope of the presentdisclosure.

FIG. 12C illustrates a cross-sectional view of some embodiments of asemiconductor device 1200C, in which the capping layer 106 has beenetched to form first and second trenches 1202C, 1204C. The first andsecond trenches 1202C, 1204C separate the capping structure 106 intofirst and second external connection portions 804A, 804B, and a capportion 806, which are not in contact with one another. Additionally,the first trench 1202C extends through the MEMS substrate 308 and intothe IMD material 304, which forms a conductive path directly from firstand second active elements 310A, 310B, through the metallization planes312, via interconnects 314, the first external connection portion 804Aof the capping structure 106, and to external circuitry. Themetallization planes 312 and the via interconnects 314 also formconnections from first and second active elements 310A, 310B to the MEMSsubstrate 308 (e.g., the first and second MEMS devices 104A, 104B)through eutectic bonds 328. The MEMS substrate (e.g., the first andsecond MEMS devices 104A, 104B) form connections to external circuitrythrough the second external connection portion 804B of the cappingstructure 106.

The MEMS substrate 308 of the semiconductor device 1200C includes spilltrenches 1206C in the formed between the eutectic bonds 328 (hermeticseals) and the first or second MEMS device 104A, 104B. The spilltrenches 1206C are configured to capture excess bonding material (i.e.,from the bottom bond pad 330 and/or the top bond pad 332 of the eutecticbonds 328), which may “squirt out” from the eutectic bonds 328 when thecapping structure 106 and the device substrate 102 are pressed togetherduring the eutectic bonding process. The spill trenches 1206C preventdamage and/or contamination to the first or second MEMS devices 104A,104B during the eutectic bonding process. Consequently, in someembodiments, at least one of the spill trenches 1206C is filled, atleast partially, with bonding material.

FIG. 12D illustrates a cross-sectional view of some embodiments of asemiconductor device 1200D including a device substrate 102, but noprocessed substrate 306. The semiconductor device 1200D contains toactive or passive elements, MEMS elements (e.g., the first and secondMEMS devices 104A, 104B), internal connections within the MEMS substrate308, and connections to external circuitry through the first and secondexternal connection portions 804A, 804B capping structure 106.

FIGS. 13A-13B illustrate cross-sectional views of various embodiments ofa semiconductor device with multiple MEMS cavities.

FIG. 13A illustrates a cross-sectional view of some embodiments of asemiconductor device 1300A, in which the MEMS substrate 308 has beenetched adjacent a sidewall 1302A of the capping layer 106 to form atrench 1304A. In alternative embodiments, the trench 1304A can be etchedthrough the capping layer 106. A shallow lateral trench 1306A isarranged at a first bonding interface 1308A 306 and 308 between theprocessed substrate 306 and the MEMS substrate 308. For the embodimentsof the semiconductor device 1300A, the first bonding interface 1308Aincludes eutectic bonds 328, which include a bottom bond pad 330 (e.g.,Al, Cu, Ti, Ta, Au, Ni, Sn) and a top bond pad 332 (e.g., Ge, Si). Inother embodiments, the first bonding interface 1308A includes fusionbonds formed from one or more bonding materials 326 (e.g., SiO₂). Thetrench 1304A and the shallow lateral trench 1306A combine to form avent, which permits a second gas pressure within the second cavity 108Bto be independently adjusted relative to a first gas pressure within thefirst cavity 108A.

The trench 1304A and the shallow lateral trench 1306A are patternedbefore bonding. After the second gas pressure within the second cavity108B is adjusted, the vent is “capped” by a first seal material 1310A,which reduces a size of the trench 1304A. In some embodiments, the firstseal material 1310A includes an oxide (e.g., SiO₂), which is disposedalong the by a CVD process such as along the sidewall 1302A of thecapping layer 106 and trench 1304A, and along the bottom of the trench1304A. A second seal material 1312A is then disposed over the first sealmaterial 1310A to achieve hermetic seal. In some embodiments, the secondseal material 1312A includes a metal (e.g., Al, Cu, etc.).

FIG. 13B illustrates a cross-sectional view of some embodiments of asemiconductor device 1300B, which is substantially similar to thesemiconductor device 1300A, in which a trench 1304B and a shallowlateral trench 1306B form a vent. However, the shallow lateral trench1306B is formed at a second bonding interface 1308B between theprocessed capping layer 106 and the MEMS substrate 308. Additionally,the shallow lateral trench 1306B is formed within a bonding material326, which forms a fusion bond between a lower surface of the cappingstructure 106 and MEMS substrate 308. In other embodiments, the shallowlateral trench 1306B is formed within a bottom surface of the bondingmaterial 326 prior to bonding. In other embodiments, the second bondinginterface 1308B is formed by fusion bonds.

Therefore, the present disclosure is directed to multiple MEMS devicesthat are integrated together on a single substrate. A device substratecomprising first and second micro-electro mechanical system (MEMS)devices is bonded to a capping structure. The capping structurecomprises a first cavity arranged over the first MEMS device and asecond cavity arranged over the second MEMS device. The first cavity isfilled with a first gas at a first gas pressure. The second cavity isfilled with a second gas at a second gas pressure, which is differentfrom the first gas pressure. A recess is arranged within a lower surfaceof the capping structure. The recess abuts the second cavity. A vent isarranged within the capping structure. The vent extends from a top ofthe recess to the upper surface of the capping structure. A lid isarranged within the vent and configured to seal the second cavity.

Some embodiments relate to a method of forming a micro-electromechanical system (MEMS) structure. The method includes providing adevice substrate comprising a first MEMS device and a second MEMSdevice, and providing a capping structure comprising a first cavity anda second cavity. The method further includes bonding the cappingstructure to the device substrate, so that the first cavity is arrangedover the first MEMS device and the second cavity is arranged over thesecond MEMS device. The method further includes establishing a firstpressure within the first cavity and the second cavity, and selectivelyetching a vent within the capping structure to change the first pressurewithin the second cavity to a second pressure, which is different fromthe first pressure.

Other embodiments relate to a method of forming a micro-electromechanical system (MEMS) structure. The method includes performing afirst etching process on a first side of a capping structure having afirst cavity and a second cavity. The first etching process forms arecess within a surface of the second cavity. The method furtherincludes bonding the capping structure to a device substrate so that thefirst cavity abuts a first MEMS device and the second cavity abuts asecond MEMS device. The method further includes performing a secondetching process on a second side of the capping structure to form a ventextending through the capping structure to the recess. The methodfurther includes forming a lid within the vent.

Still other embodiments relate to a method of forming a micro-electromechanical system (MEMS) structure. The method includes performing afirst etching process on a first side of a capping structure to form arecess within the first side of the capping structure, and coupling thecapping structure to a substrate to cause a cavity within the cappingstructure to abut a MEMS device, wherein the recess is in communicationwith the cavity. The method further includes performing a second etchingprocess on a second side of the capping structure to form a ventextending through the capping structure to the recess

While methods 200, 400, and 700 have been described as a series of actsor events, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method of forming a micro-electro mechanicalsystem (MEMS) structure, comprising: providing a device substratecomprising a first MEMS device and a second MEMS device; providing acapping structure comprising a first cavity and a second cavity; bondingthe capping structure to the device substrate, so that the first cavityis arranged over the first MEMS device and the second cavity is arrangedover the second MEMS device; establishing a first pressure within thefirst cavity and the second cavity; and selectively etching a ventwithin the capping structure to change the first pressure within thesecond cavity to a second pressure, which is different from the firstpressure.
 2. The method of claim 1, further comprising: forming a recesswithin an upper surface of the second cavity; and forming the ventwithin an upper surface of the capping structure facing away from thesecond cavity, wherein the recess and the vent collectively form anopening between the second cavity and the upper surface of the cappingstructure.
 3. The method of claim 2, wherein the vent extends outwardfrom the upper surface of the second cavity.
 4. The method of claim 2,further comprising: forming a lid within the vent.
 5. The method ofclaim 4, wherein the recess is arranged vertically between a bottommostsurface of the lid and the upper surface of the second cavity.
 6. Themethod of claim 4, wherein forming the lid comprises: forming a lidstructure within the vent and onto the upper surface of the cappingstructure; and etching the lid structure along the upper surface of thecapping structure to remove a portion of the lid structure from theupper surface of the capping structure.
 7. The method of claim 4,further comprising: changing a pressure of an ambient environmentsurrounding the capping structure from the first pressure to the secondpressure after forming the vent within the upper surface of the cappingstructure and before forming the lid within the vent.
 8. The method ofclaim 2, further comprising: performing one or more etch processes to alower surface of the capping structure opposing the upper surface of thecapping structure to form the first cavity and the second cavity; andwherein one or more etch processes simultaneously form a trench thatextends from the lower surface, through the capping structure, to theupper surface of the capping structure, and which surrounds and isolatesa pillar formed from the capping structure.
 9. The method of claim 2,wherein the opening has stepped sidewalls extending between the secondcavity and the upper surface of the capping structure.
 10. The method ofclaim 1, wherein bonding the capping structure to the device substratefurther comprises: forming a first hermetic seal, which surrounds thefirst cavity at a first interface between a lower surface of the cappingstructure and an upper surface of the device substrate; and forming asecond hermetic seal, which surrounds the second cavity at a secondinterface between the lower surface of the capping structure and theupper surface of the device substrate.
 11. A method of forming amicro-electro mechanical system (MEMS) structure, comprising: performinga first etching process on a first side of a capping structure having afirst cavity and a second cavity, wherein the first etching processforms a recess within a surface of the second cavity; bonding thecapping structure to a device substrate so that the first cavity abuts afirst MEMS device and the second cavity abuts a second MEMS device;performing a second etching process on a second side of the cappingstructure to form a vent extending through the capping structure to therecess; and forming a lid within the vent.
 12. The method of claim 11,wherein the recess has a first width that is larger than a second widthof the vent.
 13. The method of claim 11, wherein the lid has abottommost surface facing the device substrate, which is verticallyoffset from the surface of the second cavity by a non-zero distance. 14.The method of claim 11, wherein forming the lid comprises: forming a lidstructure within the vent and onto the second side of the cappingstructure; and etching the lid structure along the second side of thecapping structure to remove a portion of the lid structure from thesecond side of the capping structure.
 15. The method of claim 11,wherein the recess is arranged vertically between a bottommost surfaceof the lid and the surface of the second cavity.
 16. The method of claim11, wherein the recess and the vent collectively form an opening havingstepped sidewalls extending between the second cavity and the secondside of the capping structure.
 17. A method of forming a micro-electromechanical system (MEMS) structure, comprising: performing a firstetching process on a first side of a capping structure to form a recesswithin the first side of the capping structure; coupling the cappingstructure to a substrate to cause a cavity within the capping structureto abut a MEMS device, wherein the recess is in communication with thecavity; and performing a second etching process on a second side of thecapping structure to form a vent extending through the capping structureto the recess, wherein the recess and the vent collectively form anopening having stepped sidewalls extending between the cavity and thesecond side of the capping structure.
 18. The method of claim 17,further comprising: performing one or more etch processes to the cappingstructure to form the cavity; and performing the first etching processto form the recess within the cavity.
 19. The method of claim 17,further comprising: forming a lid within the vent and onto the secondside of the capping structure; and etching the lid along the second sideof the capping structure to remove the lid from a portion of the secondside of the capping structure.
 20. The method of claim 17, wherein thevent has a first width defined between a first pair of sidewall of thecapping structure, the recess has a second width defined between asecond pair of sidewalls of the capping structure, and the cavity has athird width defined between a third pair of sidewalls of the cappingstructure; and wherein the first width is smaller than the second widthand the second width is smaller than the third width.